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Washington Builders Limit Runoff From Record Rainfall
Record-breaking rainfall in the Northwest inundated parking lots and overwhelmed storm water management systems in Washington state two weeks ago, but the Kitsap Home Builders Association came through unscathed thanks to pervious pavements, a rain garden and other low-impact development features installed by member volunteers that kept excess water at bay.
In 48 hours, the Bremerton, Wash. area was saturated by about 13 inches of precipitation, a record even for the rainy Northwest, or at least for the city itself, said the association’s executive director, Art Castle. “When I came in to work Monday morning, the rainfall was still at its peak and I saw a river running down the street,” he said. But at the HBA headquarters, “there was no surface runoff from the site,” he said.
Low-impact development uses features that stop or slow the release of storm water from a site, enabling the water to gradually seep into the ground rather than flow from the site into a storm water or sewer system.
The HBA applied for and won a Public Involvement and Education grant from the Puget Sound Action Team to install and then demonstrate low-impact development projects. The association is also participating in an effort to develop voluntary low-impact development standards under a U.S. Environmental Protection Agency Section 319 grant that is being managed by the Washington Department of Ecology.
Association members broke ground for the project on May 1, and soon began digging up the parking lot and landscaping and replacing them with pervious pavement blocks, adding pervious concrete and asphalt, installing native plants and other drought-resistant vegetation,and putting a green roof on a storage shed. Where possible, the existing pavement was recycled to create the new surfaces, and old plants were moved to gardens in other areas.
Sixty volunteers donated time, materials and services worth $3.50 per every dollar of the $40,000 installation grant.
When the deluge arrived, the low-impact features of the site came through with flying colors, as a video that Castle posted on the HBA site demonstrates. On Monday, Dec. 3, the video shows only a trickle of rainwater leaving the HBA parking lot even as rain floods the surrounding businesses and streets.
The HBA is working on a voluntary standard for low-impact development that Bremerton and surrounding jurisdictions can use to help encourage its use. Right now, builders have an impervious surface limit of 5,000 square feet — including driveways, sidewalks and the house itself — before a requirement kicks in to hire a professional engineer to create a storm water plan, which can add costly consulting and installation fees, Castle noted.
But if the builder installs pervious pavement for the driveway, sidewalk and other outdoor surfaces, the first 5,000 square feet do not count toward the limit, potentially saving the builder and home owner thousands in fees and materials costs.
The association plans to finish the standard by the spring of 2008.
For more information, e-mail Calli Schmidt at NAHB, or call her at 800-368-5242 x8132.
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